CDC: Lyme Disease May Be Diagnosed 10 Times More Than Estimated

Recently I visited a relative on the eastern end of Long Island, about 90 miles outside New York City. The heat was brutal, and the house had no air conditioning and wasn’t accommodating to breezes — so on the first night I arrived, I sat out on the deck as the sun sank and the air cooled. Just as it became too dim to see the far end of the garden, there was a thrashing noise, as though something had gotten caught in the hedge beyond the pool, and then a whffft as whatever had tangled itself sailed over the obstacle. A moment later, something spiny but soft-edged poked into the sliver of light from the window, and bobbed, and bowed toward the ground. The spiny bits were antlers; the intruders were two white-tailed bucks, at least a year old, come to munch on the unattended lawn.

Because I am a city kid, my first thought was, “Aww, that’s pretty.” And because I am me, my next one was: “I wonder what the Lyme disease situation is out here?”

At the time, I thought I was overreacting. (Scary Disease Girl sees threats everywhere.) But news announced today by the Centers for Disease Control and Prevention makes me think I was right to be concerned. Relaying the results of research that its scientists released at a conference in Boston, the CDC said the number of cases of Lyme disease diagnosed in the United States each year may be 10 times what was previously thought.

From the CDC’s press release describing the research (I haven’t been able to find an abstract online):

This early estimate is based on findings from three ongoing CDC studies that use different methods, but all aim to define the approximate number of people diagnosed with Lyme disease each year. The first project analyzes medical claims information for approximately 22 million insured people annually for six years, the second project is based on a survey of clinical laboratories and the third project analyzes self-reported Lyme disease cases from a survey of the general public.

Each year, more than 30,000 cases of Lyme disease are reported to CDC, making it the most commonly reported tick-borne illness in the United States. The new estimate suggests that the total number of people diagnosed with Lyme disease is roughly 10 times higher than the yearly reported number. This new estimate supports studies published in the 1990s indicating that the true number of cases is between 3- and 12-fold higher than the number of reported cases.

“We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater,” said Paul Mead, M.D., M.P.H, chief of epidemiology and surveillance for CDC’s Lyme disease program. “This new preliminary estimate confirms that Lyme disease is a tremendous public health problem in the United States, and clearly highlights the urgent need for prevention.”

What’s especially interesting about this announcement is that Lyme disease surveillance in the US is based on its being a notifiable condition — that is, when a physician diagnoses a case, he or she is supposed to tell the state health department, which in turn is supposed to tell the CDC. That surveillance data, which has been flowing since Lyme was made a notifiable disease in 1991, is what forms the basis of the CDC’s estimates, captured in tables such as this one of cases by state by year and in this map:

Yet the agency clearly already knew that it wasn’t getting the full picture. On the website page that details its surveillance, the CDC adds:

Under-reporting and misclassification are features common to all surveillance systems. Not every case of Lyme disease is reported to CDC, and some cases that are reported may be due to another cause. Under-reporting is more likely to occur in highly endemic areas, whereas over-reporting is more likely to occur in non-endemic areas… Surveillance data are subject to each state’s abilities to capture and classify cases, which are dependent upon budget and personnel and varies not only between states, but also from year to year within a given state.

A 10-fold rise in Lyme would be striking enough — but illnesses carried by deer, or more precisely the ticks that feed on deer, aren’t limited to Lyme disease. (If you’ve been hanging around here a while, you’ll have read about erlichiosis, anaplasmosis, babesiosis in donated blood, Heartland virus, deer tick virus, and the tick-transmitted alpha-gal allergy to meat.) Because it emerged in the United States, sickens so many people, and is in some aspects so contentious, Lyme tends to get the tick-disease headlines. But there are other troubling tick diseases, some of which travel in the same ticks as Lyme does — and while they make people very sick, they are not as well-researched or well-recognized by physicians.

In the past month, there have been a number of new pieces of news regarding those lesser-known tickborne illnesses. They deserve attention — so rather than cram them on the bottom of today’s news, I’ll break them out in a separate post.